See how the action title handles multiple selections properly, but the GUI editor is missing for it. For input_select entities, it should just show drop down list with checkbox on each row, to allow multiple selections.
Same for triggers. Instead of simple dropdownlist, it should have checkbox dropdown, something like this:
Checkbox to allow select multiple (which is already supported by yaml, but not by GUI), and “tags” when it’s collapsed, to show all the selected values.
In the screenshot example are even categories, which are not necesary, but it would be actually great to put Unknown and Unavailable into one category, and all known states of the entity into another category.